Ceramics heater for semiconductor production system

ABSTRACT

For semiconductor manufacturing equipment a ceramic susceptor is made available in which by optimizing the inter-wiring-line separation in the resistive heating element, damage due to shorting between resistive heating element lines during heating operations is prevented while wafer-surface temperature uniformity is maintained. The ceramic susceptor ( 1 ) for semiconductor manufacturing equipment has a resistive heating element ( 3   a ) on a surface of or inside ceramic substrate ( 2 ), with the smallest angle θ formed by the bottom and lateral sides of the resistive heating element ( 3   a ) In a section of the resistive heating element ( 3   a ) being 5° or greater. A plasma electrode may be arranged on a surface of or inside the ceramic substrates ( 2   a ) of the ceramic susceptor ( 1 ). The ceramic substrates ( 2   a ) are preferably made of at least one selected from aluminum nitride, silicon nitride, aluminum oxynitride, and silicon carbide.

TECHNICAL FIELD

The present invention relates to ceramic susceptors used to hold andheat wafers in semiconductor manufacturing equipment in which specificprocesses are carried out on the wafers in the course of semiconductormanufacture.

BACKGROUND ART

Various structures have been proposed to date for ceramic susceptorsused in semiconductor manufacturing equipment. Japanese Examined Pat.App. Pub. No. H06-28258, for example, proposes a semiconductor waferheating device equipped with a ceramic susceptor that is installed in areaction chamber and has an embedded resistive heating element, and apillar-like support member that is provided on the side of the susceptorother than its wafer-heating side and forms a gastight seal between itand the chamber.

In order to reduce manufacturing costs, a transition to wafers of largerdiametric span—from 8-inch to 12-inch in outer diameter—is in progress,resulting in the diameter of the ceramic susceptor that holds the waferincreasing to 300 mm or more. At the same time, calls are forwafer-surface temperature deviation—i.e., temperature uniformity—to bewithin ±1.0%, and preferably within ±0.5%, in a wafer loaded on theceramic susceptor and being heated by the resistive heating element, towhich current is being supplied.

Patent Reference 1

Japanese Examined Pat. App. Pub. No. H06-28258.

The pattern of the resistive heating element formed on the surface of orinside the ceramic susceptor is designed and arranged so as to uniformlyheat the surface on which the wafer is supported. More specifically, oneconceivable way to improve wafer-surface temperature uniformity would beto arrange the resistive heating element densely by narrowing to theutmost the linewidth of and adjacent inter-line spacing in the resistiveheating element.

However, if in laying stress on improving wafer-surface temperatureuniformity the spacing of the resistive-heating-element wiring isnarrowed too far, a partial discharge phenomenon arises from thepotential difference created between wiring lines of the resistiveheating element. If this partial discharge phenomenon advances further,shorting occurs between the resistive-heating-element wiring lines,resulting in damage to the ceramic susceptor.

DISCLOSURE OF INVENTION

An object of the present invention, in view of such circumstances todate, is to optimize the design of the resistive-heating-element patternand thereby make available for semiconductor manufacturing equipment aceramic susceptor that while maintaining wafer-surface temperatureuniformity makes for preventing susceptor damage due to shorting betweenresistive heating element lines during heating operations.

To achieve this object the present invention provides, for semiconductormanufacturing equipment, a ceramic susceptor having a resistive heatingelement on a surface of or inside a ceramic substrate, and characterizedby the minimum angle formed by bottom and lateral faces in a sectionthrough the resistive heating element being 5° or more.

When a wafer is placed on the wafer support surface of this ceramicsusceptor for semiconductor manufacturing equipment and the resistiveheating element is energized and heated, variation in the wafer surfacetemperature is preferably ±1.0% or less, and further preferably ±0.5% orless, at the working temperature.

Furthermore, the ceramic substrates of this ceramic susceptor forsemiconductor manufacturing equipment are preferably made from a ceramicselected from at least one of the following materials: aluminum nitride,silicon nitride, aluminum oxynitride, and silicon carbide. Yet furtherpreferably, the ceramic substrates are aluminum nitride or siliconcarbide substrates with thermal conductivity of 100 W/m·K or greater.

Furthermore, the resistive heating element of this ceramic susceptor forsemiconductor manufacturing equipment is preferably made from at leastone metal selected from tungsten, molybdenum, platinum, palladium,silver, nickel, and chrome.

A plasma electrode may further be disposed on a surface of or inside theceramic substrate of this ceramic susceptor for semiconductormanufacturing equipment.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic section diagram of a resistive heating element ina ceramic susceptor, FIG. 1(a) showing an actual resistive heatingelement in section, and FIG. 1(b) showing an ideal resistive heatingelement in section;

FIG. 2 is a schematic section diagram of a ceramic susceptor accordingto a preferred embodiment of the present invention; and

FIG. 3 is a schematic section diagram of a ceramic susceptor accordingto another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Having studied in detail phenomena in which cracking and like damageoccurs in ceramic susceptors when the susceptor temperature is elevatedby passing current into its resistive heating element, the presentinventors discovered that resistive-heating-element wiring lines thatneighbor each other short in regions where their difference in potentialis greatest, leading to damage to the susceptor.

To avert this sort of shorting phenomenon in the resistive heatingelement, the present inventors focused their attention on the sectionalform of the resistive heating element, and especially on the angleformed by the bottom and lateral faces in a section through theresistive-heating-element wiring lines (also referred to simply as“resistive-heating-element section” hereinafter). More specifically,whether this shorting phenomenon is present or not is determined by theseparation between the wiring lines of the resistive heating element,the applied voltage, the form of the electrodes, and the atmosphericpressure. The inter-line separation is limited by designing theresistive-heating-element pattern to gain temperature uniformity in thesusceptor, while the applied voltage and atmospheric pressure aredetermined by the process conditions.

If the inter-line separation of the resistive heating element isconstant, shorting is least likely to occur when the line section issquare- or rectangular-shaped, while shorting is most likely to occurwhen the line section is needle shaped. Based on the thinking thatcracks caused by shorting could be prevented by how the sectional formof the susceptor resistive heating element is devised, ways of doingthis were investigated.

The resistive heating element of a ceramic susceptor is generally formedby printing and firing a conductive paste onto a sintered ceramiccompact or green sheet. When the sectional shape of the resultingresistive heating element is shown schematically, it is usuallypresented with the rectilinear shape of an ideal resistive heatingelement 3 b as shown in FIG. 1(b). In actuality, however, the resistiveheating element 3 a always has a basically trapezoidal shape withinclined sides as shown in FIG. 1(a), due to sagging or spreading of theconductive paste, and the smallest angle θ formed by the lateral sidesand bottom of the resistive heating element 3 a contacting the ceramicsubstrate 2 is acute.

Given these factors, presence/absence of shorting between wiring lineswhen the resistive heating element is drawing current/heating wasinvestigated by varying the inter-line separation L of the resistiveheating element 3 a in the resistive heating element section indicatedin FIG. 1(b) in a range of 0.5 mm to 20 mm, and meanwhile setting thesmallest angle θ formed by the bottom and lateral faces of the resistiveheating element larger in stages starting with 2°. As a result, it wasfound that regardless of the inter-line separation L, shorting betweenlines can be averted by having the smallest angle θ formed by the bottomand lateral sides in the resistive heating element section be 5° orgreater.

Here, to change the smallest angle θ formed by the bottom and lateralsides in the resistive heating element section, a method such aschanging the paste dilution to adjust paste viscosity when print-coatingthe paste for resistive-heating-element formation may be adopted.

In a ceramic susceptor according to the present invention, even with thesmallest angle θ formed by the bottom and sides of the resistive heatingelement being 5° or greater, care that the inter-line separation L ofthe resistive heating element is not too small, i.e., generally that theinter-line separation L is not less than 0.1 mm, is needed becauseotherwise shorting between lines is liable to occur.

Using a ceramic susceptor in which the smallest angle θ formed by thebottom and sides in the resistive heating element section is 5° orgreater according to the present invention, deviation (i.e., temperatureuniformity) in the wafer surface temperature when the resistive heatingelement is drawing current/heating can be brought advantageously towithin ±1.0%, and more advantageously to within ±0.5%, at the workingtemperature.

If the inter-line separation L of the resistive heating element is toolarge, however, deviation in the wafer surface temperature when theresistive heating element is drawing current/heating grows greater,making it difficult to achieve desired temperature uniformity. Theinter-line separation L of the resistive heating element is thereforepreferably 5 mm or less.

The specific structure of a ceramic susceptor according to the presentinvention is described next with reference to FIG. 2 and FIG. 3. Theceramic susceptor 1 shown in FIG. 2 has a resistive heating element 3with a prescribed wiring pattern provided on one surface of a ceramicsubstrate 2 a, and a separate ceramic substrate 2 b bonded to the samesurface of the ceramic substrate 2 a by means of an adhesive layer 4 ofglass or ceramic. Here, the linewidth in the wiring pattern of theresistive heating element 3 is preferably rendered to be 5 mm or less,and more preferably 1 mm or less.

The ceramic susceptor 11 shown in FIG. 3 is furnished with an internalresistive heating element 13 and a plasma electrode 15. Morespecifically, a ceramic substrate 12 a having the resistive heatingelement 13 on one surface thereof and a ceramic substrate 12 b arebonded by an adhesive layer 14 a similarly as with the ceramic susceptorshown in FIG. 2. At the same time, a separate ceramic substrate 12 cprovided with a plasma electrode 15 is bonded to the other side of theceramic substrate 12 a by means of a glass or ceramic adhesive layer 14b.

It should be understood that instead of bonding respective ceramicsubstrates to manufacture the ceramic susceptors, the ceramic susceptorsshown in FIG. 2 and FIG. 3 can alternatively be manufactured bypreparing approximately 0.5 mm thick green sheets, print-coating aconductive paste in the circuit pattern of the resistive heating elementand/or plasma electrode on respective green sheets, laminating thesegreen sheets together with other green sheets as needed to achieve therequired thickness, and then simultaneously sintering the multiple greensheets to unite them.

Embodiments Embodiment 1

A sintering additive and a binder were added to, and dispersed into andmixed with, aluminum nitride (AlN) powder using a ball mill. Theresulting powder blend was dried with a spray dryer and thenpress-molded into 1-mm thick, 380-mm diameter disks. The molded diskswere degreased in a non-oxidizing atmosphere at a temperature of 800°C., and then sintered for 4 hours at 1900° C., producing sintered AlNcompacts. The thermal conductivity of the resulting AlN sinters was 170W/mK. The circumferential surface of each sintered AlN compact was thenpolished to an outside diameter of 300 mm to prepare two AlN substratesfor a ceramic susceptor.

A paste of tungsten powder and sintering additive kneaded together witha binder was then print-coated on the surface of one of these AlNsubstrates to form a predetermined pattern for theresistive-heating-element wiring lines. The printing screen and pasteviscosity were varied to change in the resistive heating element insection the adjoining inter-line separation L and the smallest angle θformed by the bottom and lateral sides of the resistive heating element(termed “sectional smallest angle θ” below). The resulting AlN substratewas degreased in a non-oxidizing atmosphere at a temperature of 800° C.and then baked at 1700° C., producing a tungsten resistive heatingelement.

A paste of Y₂O₃ adhesive agent kneaded with a binder was print-coated onthe surface of the remaining AlN substrate, which was then degreased at500° C. The adhesive layer of this AlN substrate was then overlaid onthe side of the AlN substrate on which the resistive heating element wasformed, and the substrates were bonded by heating at 800° C. Sampleceramic susceptors having the FIG. 1 configuration and differing ininter-line separation L and sectional smallest angle θ as set forth inthe following Table I were thus produced.

The temperature of each sample susceptor produced in this way was thenraised to 500° C. by flowing a current at a voltage of 200 V into theresistive heating element through two electrodes formed on the surfaceof the susceptor opposite the wafer-support side, and the susceptorswere checked for presence/absence of cracking occurrences. In addition,a 0.8-mm thick, 300-mm diameter silicon wafer was placed on thewafer-support side of the ceramic susceptor, and the temperaturedistribution in the wafer surface was measured to find the temperatureuniformity at 500° C. The results obtained are set forth for each samplein Table I below. TABLE I Sectional Inter-line Susceptor crackingWafer-surface smallest separation occurrence freq. 500° C. temp. Sampleangle θ (°) L (mm) (N = 5) uniformity (° C.)  1 7 20 0/5 ±1.80  2 7 100/5 ±1.31  3 7 5 0/5 ±0.48  4 7 1 0/5 ±0.40  5 7 0.5 0/5 ±0.35  6 5 200/5 ±1.80  7 5 10 0/5 ±1.31  8 5 5 0/5 ±0.48  9 5 1 0/5 ±0.40 10 5 0.50/5 ±0.35  11* 4 20 0/5 ±1.80  12* 4 10 0/5 ±1.31  13* 4 5 2/5 ±0.48 14* 4 1 4/5 ±0.40  15* 4 0.5 5/5 ±0.35  16* 2 20 0/5 ±1.80  17* 2 102/5 ±1.31  18* 2 5 4/5 ±0.48  19* 2 1 4/5 ±0.40  20* 2 0.5 5/5 ±0.35Note:Samples marked with an asterisk (*) in the table are comparativeexamples.

As will be understood from the results set forth in Table I, susceptorcracking during heating/temperature elevation could be eliminated in analuminum nitride ceramic susceptor by the sectional smallest angle θ ofthe resistive heating element being 5° or greater. It is also evidentthat temperature uniformity of within ±0.5% was achieved by theinter-line separation L of the resistive heating element being withinthe range 0.5 mm to 5 mm.

Embodiment 2

A sintering additive and a binder were added to, and dispersed into andmixed with, silicon nitride (Si₃N₄) powder using a ball mill. Theresulting powder blend was dried with a spray dryer and thenpress-molded into 1-mm thick, 380-mm diameter disks. The molded diskswere degreased in a non-oxidizing atmosphere at a temperature of 800°C., and then sintered for 4 hours at 1550° C., producing sintered Si₃N₄compacts. The thermal conductivity of the resulting Si₃N₄ sinters was 20W/mK. The circumferential surface of each sintered Si₃N₄ compact wasthen polished to an outside diameter of 300 mm to prepare two Si₃N₄substrates for a ceramic susceptor.

A paste of tungsten powder and sintering additive kneaded together witha binder was then print-coated on the surface of one of these Si₃N₄substrates to form a predetermined pattern for theresistive-heating-element wiring lines. The printing screen and pasteviscosity were varied to change in the resistive heating element insection the adjoining inter-line separation L and the smallest angle 0.This Si₃N₄ substrate was then degreased in a non-oxidizing atmosphere ata temperature of 800° C. and then baked at 1700° C., producing atungsten resistive heating element.

A paste of SiO₂ adhesive agent kneaded with binder was print-coated onthe surface of the other Si₃N₄ substrate, which was then degreased at500° C. The adhesive layer of this Si₃N₄ substrate was then overlaid onthe side of the Si₃N₄ substrate on which the resistive heating elementwas formed, and the substrates were bonded by heating at 800° C. Sampleceramic susceptors having the FIG. 1 configuration and differing ininter-line separation L and sectional smallest angle θ as set forth inthe following Table II were thus produced.

The temperature of each sample susceptor produced in this way was thenraised to 500° C. by flowing a current at a voltage of 200 V into theresistive heating element, and the susceptors were checked forpresence/absence of cracking occurrences. In addition, a 0.8-mm thick,300-mm diameter silicon wafer was placed on the wafer-support side ofthe ceramic susceptor, and the temperature distribution in the wafersurface was measured to find the temperature uniformity at 500° C. Theresults obtained are set forth for each sample in Table II below. TABLEII Sectional Inter-line Susceptor cracking Wafer-surface smallestseparation occurrence freq. 500° C. temp. Sample angle θ (°) L (mm) (N =5) uniformity (° C.) 21 7 20 0/5 ±2.85 22 7 10 0/5 ±2.50 23 7 5 0/5±0.91 24 7 1 0/5 ±0.81 25 7 0.5 0/5 ±0.67 26 5 20 0/5 ±2.85 27 5 10 0/5±2.50 28 5 5 0/5 ±0.91 29 5 1 0/5 ±0.81 30 5 0.5 0/5 ±0.67  31* 4 20 0/5±2.85  32* 4 10 0/5 ±2.50  33* 4 5 1/5 ±0.91  34* 4 1 3/5 ±0.81  35* 40.5 4/5 ±0.67  36* 2 20 0/5 ±2.85  37* 2 10 2/5 ±2.50  38* 2 5 4/5 ±0.91 39* 2 1 5/5 ±0.81  40* 2 0.5 5/5 ±0.67Note:Samples marked with an asterisk (*) in the table are comparativeexamples.

As will be understood from Table II, in a silicon nitride ceramicsusceptor also, as was likewise the case with the aluminum nitridemanufacture of Embodiment 1, susceptor heating/temperature-elevationcracking could be eliminated by the sectional smallest angle θ of theresistive heating element being 5° or greater. Furthermore, temperatureuniformity of within ±1.0% was achieved by the inter-line separation Lof the resistive heating element being within the range 0.5 mm to 5 mm.

Embodiment 3

A sintering additive and a binder were added to, and dispersed into andmixed with, aluminum oxynitride (AlON) powder using a ball mill. Theresulting powder blend was dried with a spray dryer and thenpress-molded into 1-mm thick, 380-mm diameter disks. The molded diskswere degreased in a non-oxidizing atmosphere at a temperature of 800°C., and then sintered for 4 hours at 1770° C., producing sintered AlONcompacts. The thermal conductivity of the resulting AlON sinters was 20W/mK. The circumferential surface of each sintered AlON compact was thenpolished to an outside diameter of 300 mm to prepare two AlON substratesfor a ceramic susceptor.

A paste of tungsten powder and sintering additive kneaded together witha binder was then print-coated on the surface of one of these AlONsubstrates to form a predetermined pattern for theresistive-heating-element wiring lines. The printing screen and pasteviscosity were varied to change in the resistive heating element insection the adjoining inter-line separation L and the smallest angle θ.This AlON substrate was then degreased in a non-oxidizing atmosphere ata temperature of 800° C. and then baked at 1700° C., producing atungsten resistive heating element.

A paste of SiO₂ adhesive agent kneaded with a binder was print-coated onthe surface of the other AlON substrate, which was then degreased at500° C. The adhesive layer of this AlON substrate was then overlaid onthe side of the AlON substrate on which the resistive heating elementwas formed, and the substrates were bonded by heating at 800° C. Sampleceramic susceptors having the FIG. 1 configuration and differing ininter-line separation L and sectional smallest angle θ as set forth inthe following Table III were thus produced.

The temperature of each sample susceptor produced in this way was thenraised to 500° C. by flowing a current at a voltage of 200 V into theresistive heating element, and the susceptors were checked forpresence/absence of cracking occurrences. In addition, a 0.8-mm thick,300-mm diameter silicon wafer was placed on the wafer-support side ofthe ceramic susceptor, and the temperature distribution in the wafersurface was measured to find the temperature uniformity at 500° C. Theresults obtained are set forth for each sample in Table III below. TABLEIII Sectional Inter-line Susceptor cracking Wafer-surface smallestseparation occurrence freq. 500° C. temp. Sample angle θ (°) L (mm) (N =5) uniformity (° C.) 41 7 20 0/5 ±2.85 42 7 10 0/5 ±2.50 43 7 5 0/5±0.91 44 7 1 0/5 ±0.81 45 7 0.5 0/5 ±0.67 46 5 20 0/5 ±2.85 47 5 10 0/5±2.50 48 5 5 0/5 ±0.91 49 5 1 0/5 ±0.81 50 5 0.5 0/5 ±0.67  51* 4 20 0/5±2.85  52* 4 10 0/5 ±2.50  53* 4 5 3/5 ±0.91  54* 4 1 4/5 ±0.81  55* 40.5 5/5 ±0.67  56* 2 20 0/5 ±2.85  57* 2 10 2/5 ±2.50  58* 2 5 4/5 ±0.91 59* 2 1 5/5 ±0.81  60* 2 0.5 5/5 ±0.67Note:Samples marked with an asterisk (*) in the table are comparativeexamples.

As will be understood from Table III, in an aluminum oxynitride ceramicsusceptor also, as was likewise the case with the aluminum nitridemanufacture of Embodiment 1, susceptor heating/temperature-elevationcracking could be eliminated by the sectional smallest angle θ of theresistive heating element being 5° or greater. Furthermore, temperatureuniformity of within ±1.0% was achieved by the inter-line separation Lof the resistive heating element being within the range 0.5 mm to 5 mm.

Embodiment 4

Pairs of AlN substrates for a ceramic susceptor with a 300 mm outsidediameter were prepared from an aluminum nitride sinter using the samemethod described in Embodiment 1. When sample ceramic susceptors weremade using these AlN substrate pairs, other than changing the materialof the resistive heating element formed on the surface of one AlNsubstrate to Mo, to Pt, to Ag—Pd, and to Ni—Cr, W resistive heatingelements differing in inter-line separation Land sectional smallestangle θ were formed in the same way as in Embodiment 1.

A SiO₂ glass bonding agent was then coated over the surface of theremaining AlN substrate in each pair, and degreased in a non-oxidizingatmosphere at 800° C. The adhesive glass layer of this AlN substrate wasthen overlaid on the side of the other AlN substrate on which theresistive heating element was formed, and the substrate pairs werebonded by heating at 800° C., thereby producing ceramic susceptors ofAlN differing in inter-line separation L and sectional smallest angle θas set forth in the following Table IV.

The temperature of each sample susceptor produced in this way was thenraised to 500° C. by flowing a current at a voltage of 200 V into theresistive heating element, and the susceptors were checked forpresence/absence of cracking occurrences. In addition, a 0.8-mm thick,300-mm diameter silicon wafer was placed on the wafer-support side ofthe ceramic susceptor, and the temperature distribution in the wafersurface was measured to find the temperature uniformity at 500° C. Theresults obtained are set forth for each sample in Table IV below. TABLEIV Susceptor Wafer-surface Sectional Inter-line cracking 500° C. temp.Heating smallest separation occurrence uniformity Sample element angle θ(°) L (mm) freq. (N = 5) (° C.) 61 Mo 7 10 0/5 ±1.28 62 Mo 7 0.5 0/5±0.35 63 Mo 5 10 0/5 ±1.28 64 Mo 5 5 0/5 ±0.45 65 Mo 5 1 0/5 ±0.37 66 Mo5 0.5 0/5 ±0.35  67* Mo 4 10 0/5 ±1.28  68* Mo 4 1 2/5 ±0.37  69* Mo 40.5 5/5 ±0.35 70 Pt 7 10 0/5 ±1.28 71 Pt 7 0.5 0/5 ±0.35 72 Pt 5 10 0/5±1.28 73 Pt 5 5 0/5 ±0.45 74 Pt 5 1 0/5 ±0.37 75 Pt 5 0.5 0/5 ±0.35  76*Pt 4 10 0/5 ±1.28  77* Pt 4 1 4/5 ±0.37  78* Pt 4 0.5 4/5 ±0.35 79 Ag—Pd7 10 0/5 ±1.28 80 Ag—Pd 7 0.5 0/5 ±0.35 81 Ag—Pd 5 10 0/5 ±1.28 82 Ag—Pd5 5 0/5 ±0.45 83 Ag—Pd 5 1 0/5 ±0.37 84 Ag—Pd 5 0.5 0/5 ±0.35  85* Ag—Pd4 10 0/5 ±1.28  86* Ag—Pd 4 1 3/5 ±0.37  87* Ag—Pd 4 0.5 4/5 ±0.35 88Ni—Cr 7 10 0/5 ±1.28 89 Ni—Cr 7 0.5 0/5 ±0.35 90 Ni—Cr 5 10 0/5 ±1.28 91Ni—Cr 5 5 0/5 ±0.45 92 Ni—Cr 5 1 0/5 ±0.37 93 Ni—Cr 5 0.5 0/5 ±0.35  94*Ni—Cr 4 10 0/5 ±1.28  95* Ni—Cr 4 1 3/5 ±0.37  96* Ni—Cr 4 0.5 5/5 ±0.35Note:Samples marked with an asterisk (*) in the table are comparativeexamples.

As will be understood from Table IV, also in an aluminum oxynitrideceramic susceptor having a resistive heating element made of Mo, Pt,Ag—Pd, or Ni—Cr, as was likewise the case with the tungsten resistiveheating elements set forth in Embodiment 1, susceptorheating/temperature-elevation cracking could be eliminated by thesectional smallest angle θ of the resistive heating element being 50 orgreater. Furthermore, temperature uniformity of within ±0.5% wasachieved by the inter-line separation L of the resistive heating elementbeing within the range 0.5 mm to 5 mm.

Embodiment 5

A sintering additive, a binder, a dispersing agent and alcohol wereadded to an aluminum nitride (AlN) powder and kneaded into a paste,which was then formed using a doctor blade technique into green sheetsapproximately 0.5 mm thick.

Next the green sheets were dried for 5 hours at 80° C. A paste oftungsten powder and sintering additive kneaded together with a binderwas then print-coated on the surface of single plies of the green sheetsto form a resistive-heating-element layer in a predetermined circuitpattern. The printing screen and paste viscosity were varied to changein the resistive heating element in section the adjoining inter-lineseparation L and the smallest angle θ.

Second plies of the green sheets were likewise dried and the sametungsten paste was print-coated onto a surface thereof to form a plasmaelectrode layer. These two plies of green sheets each having aconductive layer were then laminated in a total 50 plies with greensheets that were not printed with a conductive layer, and the laminateswere united by heating them at a temperature of 140° C. while applyingpressure of 70 kg/cm².

The resulting laminates were degreased for 5 hours at 600° C. in anon-oxidizing atmosphere, then hot-pressed at 1800° C. while applyingpressure of 100 to 150 kg/cm², thereby producing 3 mm thick AlN plates.These plates were then cut to form 380-mm diameter disks, and theperiphery of each disk was polished to a 300 mm diameter. Sample ceramicsusceptors having the FIG. 2 configuration internal featuring a tungstenresistive heating element and plasma electrode and differing ininter-line separation L and sectional smallest angle θ as set forth inthe following Table V were thus produced.

The temperature of each sample susceptor produced in this way was thenraised to 500° C. by flowing a current at a voltage of 200 V into theresistive heating element, and the susceptors were checked forpresence/absence of cracking occurrences. In addition, a 0.8-mm thick,300-mm diameter silicon wafer was placed on the wafer-support side ofthe ceramic susceptor, and the temperature distribution in the wafersurface was measured to find the temperature uniformity at 500° C. Theresults obtained are set forth for each sample in Table V below. TABLE VSectional Inter-line Susceptor cracking Wafer-surface smallestseparation occurrence freq. 500° C. temp. Sample angle θ (°) L (mm) (N =5) uniformity (° C.) 97 7 20 0/5 ±1.86 98 7 10 0/5 ±1.29 99 7 5 0/5±0.47 100 7 1 0/5 ±0.41 101 7 0.5 0/5 ±0.36 102 5 20 0/5 ±1.86 103 5 100/5 ±1.29 104 5 5 0/5 ±0.47 105 5 1 0/5 ±0.41 106 5 0.5 0/5 ±0.36 107 420 0/5 ±1.86 108 4 10 0/5 ±1.29 109 4 5 4/5 ±0.47 110 4 1 4/5 ±0.41 1114 0.5 4/5 ±0.36 112 2 20 0/5 ±1.86 113 2 10 0/5 ±1.29 114 2 5 4/5 ±0.47115 2 1 5/5 ±0.41 116 2 0.5 5/5 ±0.36

As will be understood from the results shown in Table V, even withaluminum nitride ceramic susceptors having both an internal resistiveheating element and a plasma electrode, susceptorheating/temperature-elevation cracking could be eliminated by thesectional smallest angle θ of the resistive heating element being 5° orgreater. Furthermore, temperature uniformity of within ±0.5% wasachieved by the inter-line separation L of the resistive heating elementbeing within the range 0.5 mm to 5 mm.

INDUSTRIAL APPLICABILITY

In accordance with the present invention, optimizing the angle betweenthe bottom and lateral faces of the resistive heating element in sectionmakes available for semiconductor manufacturing equipment a ceramicsusceptor in which, while wafer-surface temperature uniformity ismaintained, there is no susceptor damage due to shorting betweenresistive heating element lines during heating operations.

1. For semiconductor manufacturing equipment, a ceramic susceptorcomprising: a ceramic substrate defining a wafer-support side, and aresistive heating element composed of wiring lines, defining bottom andlateral sides, in a predetermined configuration provided on either asurface of or inside a said ceramic substrate, said resistive heatingelement being configured so that in section through said wiring linesthe smallest angle formed by the bottom and lateral sides is 5° orgreater.
 2. A ceramic susceptor as set forth in claim 1, wherein when awafer is placed on the wafer support side and said resistive heatingelement is drawing current and heated deviation in the wafer surfacetemperature is ±1.0% or less at working temperature.
 3. A ceramicsusceptor as set forth in claim 2, wherein deviation in the wafersurface temperature is within ±0.5% at working temperature.
 4. A ceramicsusceptor as set forth in claim 1, wherein said ceramic substrate ismade of at least one ceramic selected from aluminum nitride, siliconnitride, aluminum oxynitride and silicon carbide.
 5. A ceramic susceptoras set forth in claim 1 wherein said ceramic substrate is eitheraluminum nitride or silicon carbide of 100 W/m·K or greater thermalconductivity.
 6. A ceramic susceptor as set forth in claim 1, whereinsaid resistive heating element is made from at least one metal selectedfrom tungsten, molybdenum, platinum, palladium, silver, nickel andchrome.
 7. A ceramic susceptor as set forth in any claim 1, furthercomprising a plasma electrode is disposed either on a surface of orinside said ceramic substrate.
 8. A ceramic susceptor as set forth inclaim 2, wherein said ceramic substrate is made of at least one ceramicselected from aluminum nitride, silicon nitride, aluminum oxynitride andsilicon carbide.
 9. A ceramic susceptor as set forth in claim 3, whereinsaid ceramic substrate is made of at least one ceramic selected fromaluminum nitride, silicon nitride, aluminum oxynitride and siliconcarbide.
 10. A ceramic susceptor as set forth in claim 9, wherein saidceramic substrate is either aluminum nitride or silicon carbide of 100W/m·K or greater thermal conductivity.
 11. A ceramic susceptor as setforth in claim 10, wherein said resistive heating element is made fromat least one metal selected from tungsten, molybdenum, platinum,palladium, silver, nickel and chrome.
 12. A ceramic susceptor as setforth in any claim 2, further comprising a plasma electrode disposedeither on a surface of or inside said ceramic substrate.
 13. A ceramicsusceptor as set forth in any claim 4, further comprising a plasmaelectrode disposed either on a surface of or inside said ceramicsubstrate.
 14. A ceramic susceptor as set forth in any claim 11, furthercomprising a plasma electrode disposed either on a surface of or insidesaid ceramic substrate.